The present invention relates to a method and apparatus for treating water and the ground which has been contaminated by hydrocarbon and halogenated hydrocarbon materials. The treatment of the contaminated ground water is accomplished by microorganisms which can biodegrade the hydrocarbon and halogenated hydrocarbon contaminants. The treatment takes place both in situ and outside of the earth in containment areas. The term "hydrocarbon" for the purpose of this application is intended to include halogenated hydrocarbons.
In cases where there are spills of hydrocarbon material into or onto the ground, the materials will contaminate the surrounding ground water through action of the natural movement of water through the ground. If the spills are not isolated and the material somehow removed, the contaminants will spread beyond the original spill area through the ground water system thereby endangering water supplies. In order to avoid this result, the contaminated material must be removed. However, few options are available to remove it. In some cases, physical removal and disposal or treatment of the soil is required. Alternatively, the spill site may be isolated to a depth below which the spill traveled via ground water action, and the contaminants retained in this area of ground isolated from surrounding areas. However, these methods are exceedingly expensive and do not eliminate the contaminants but transfer them from one site to another.
An alternative method usable in some areas where soil and climate conditions permit is to encourage the growth of natural microorganisms in the soil and ground water which are capable of biodegrading the particular hydrocarbon contaminant spilled. To some extent, the growth of the appropriate microorganisms occurs naturally when the feedstock (the spilled hydrocarbon materials) is available. It has also been shown that by increasing the presence of certain nutrients and the oxygen level in the water flowing through contaminated soil, the biodegradation process will advance more rapidly. One such process is shown in U.S. Pat. No. 3,846,290 issued Nov. 5, 1974, which teaches the addition of nutrients and oxygen to contaminated ground water. A disadvantage of this process is that the contaminants are not completely removed. Therefore, in order to avoid contamination of the surrounding area, the polluted ground water must be pumped from the ground and disposed of. This is a serious and expensive problem, since large quantities of ground water are being treated and have very dilute concentrations of contaminants. Moreover, the process is very slow because the biodegradation takes place throughout a large volume of soil. In addition, the biodegradation process is limited by the ambient conditions, e.g., temperature of the ground water and the amount of nutrients and oxygen which can filter through the affected soil. The soil structure and the natural rate of movement of water through the soil can retard biological activity and increase tremendously the amount of time taken to effectively treat contaminants in the ground.
Therefore, there is a need for a method to isolate a hydrocarbon spill to biodegrade the hydrocarbon contaminants adequately and inexpensively and to dispose of the contaminants without merely removing them by flushing the soil and disposing of them outside of the immediate spill area.